From patchwork Wed Nov 10 23:00:12 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Kjos X-Patchwork-Id: 12613561 X-Patchwork-Delegate: paul@paul-moore.com Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4610C433FE for ; Wed, 10 Nov 2021 23:00:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD82261268 for ; Wed, 10 Nov 2021 23:00:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234097AbhKJXDJ (ORCPT ); Wed, 10 Nov 2021 18:03:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46300 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234121AbhKJXDF (ORCPT ); Wed, 10 Nov 2021 18:03:05 -0500 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 730FBC061205 for ; Wed, 10 Nov 2021 15:00:17 -0800 (PST) Received: by mail-pf1-x44a.google.com with SMTP id z19-20020aa79593000000b0049472f5e52dso2747546pfj.13 for ; Wed, 10 Nov 2021 15:00:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=2l2vfSk9noud27fza1jTmzfBpZWxrMJkzDQXI8UVNOI=; b=ck6Z8uYzej/4+oPc/kvulx+Et7Mr8ngkMyTs+OcSpmwgkcmIKy5CxaT6eB1o4Dw/bD +LF7Hlf0cU44kBTUJe8ctxy7W434zCe0EKUDc+gtcizY4OeAyKYuadHviz426NuTiJHg qE62VPjHShdVR0UndKg5W07O7DMIcUywM8RffPODtyqXEcnUSSIVzx3/xFhDH3DR1u7L 5S0LUc7UJ2gyDCpNK+7OBshsQg/VXADB2lt2EV1djOL8gj8EZCgWe8mSczrNeU/u3uRJ ipcDUcRi7OG8KPx+t4FWf3FiY27EikOPxB9D6++N3I5hxqDg8LiPUGc+XhufXTILzfvx jlvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=2l2vfSk9noud27fza1jTmzfBpZWxrMJkzDQXI8UVNOI=; b=Hd026/FxJr7+w8ESKDz+YWUZRw4uSNjZSjXdpvCTep6hnvJ8Jh2tXEk+IYZu8OnKGL fRyS+wQnyY+V4GNEGlGST23kFOXQzUxe8G/CmT3MTd1mKhDGkR6fuY4737f/wconsgnR EWq0rfWWObyOa4L6YWFBM3Gza2EfEU5SH277YOD5dUvBHVdpUPevIdKKt1KmBmaNERiY sLbmHQo6obm2y3Ep7G1pPymbTGsiD3CaJONRRyAfOWbmgjlI0N5ZPcRxprAjqEpwTE8e 8jBQIgDXspbe5WOrEqcD06X/41NYnzpe7BxcDSyWhTGjjVnCIlRP7JYsA33+cB7QmS4W X2Fw== X-Gm-Message-State: AOAM532SdGXHmlbwfmkbDxzYIbWBgVhcCmjsAuPamZa1c4vZlaTF5sxG YR4IW+jTegL+77jWd6qauR5mBgaasA== X-Google-Smtp-Source: ABdhPJyNhiR0WCLprzojB+bzsoIu+VAQJAFJNw45gZ1HbjTQT04eNyWkTiTQyluaemVlbTwtyhfRpHxe7Q== X-Received: from tkjos-desktop.mtv.corp.google.com ([2620:15c:211:200:4a73:99b6:9694:8c4d]) (user=tkjos job=sendgmr) by 2002:a17:903:1c3:b0:142:3ae:5c09 with SMTP id e3-20020a17090301c300b0014203ae5c09mr2835269plh.52.1636585216973; Wed, 10 Nov 2021 15:00:16 -0800 (PST) Date: Wed, 10 Nov 2021 15:00:12 -0800 Message-Id: <20211110230013.3271596-1-tkjos@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.34.0.rc0.344.g81b53c2807-goog Subject: [PATCH 4.19 1/2] binder: use euid from cred instead of using task From: Todd Kjos To: stable@vger.kernel.org, gregkh@linuxfoundation.org, arve@android.com, tkjos@android.com, maco@android.com, christian@brauner.io, jmorris@namei.org, serge@hallyn.com, paul@paul-moore.com, stephen.smalley.work@gmail.com, eparis@parisplace.org, keescook@chromium.org, jannh@google.com, jeffv@google.com, zohar@linux.ibm.com, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, devel@driverdev.osuosl.org Cc: joel@joelfernandes.org, kernel-team@android.com, Todd Kjos , Casey Schaufler Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org commit 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b upstream. Save the 'struct cred' associated with a binder process at initial open to avoid potential race conditions when converting to an euid. Set a transaction's sender_euid from the 'struct cred' saved at binder_open() instead of looking up the euid from the binder proc's 'struct task'. This ensures the euid is associated with the security context that of the task that opened binder. Cc: stable@vger.kernel.org # 4.4+ Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") Signed-off-by: Todd Kjos Suggested-by: Stephen Smalley Suggested-by: Jann Horn Acked-by: Casey Schaufler Signed-off-by: Paul Moore Change-Id: I91922e7f359df5901749f1b09094c3c68d45aed4 --- drivers/android/binder.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index cda4f7eb58ea..58e497db26b4 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -483,6 +483,9 @@ enum binder_deferred_state { * @files files_struct for process * (protected by @files_lock) * @files_lock mutex to protect @files + * @cred struct cred associated with the `struct file` + * in binder_open() + * (invariant after initialized) * @deferred_work_node: element for binder_deferred_list * (protected by binder_deferred_lock) * @deferred_work: bitmap of deferred work to perform @@ -529,6 +532,7 @@ struct binder_proc { struct task_struct *tsk; struct files_struct *files; struct mutex files_lock; + const struct cred *cred; struct hlist_node deferred_work_node; int deferred_work; bool is_dead; @@ -2962,7 +2966,7 @@ static void binder_transaction(struct binder_proc *proc, t->from = thread; else t->from = NULL; - t->sender_euid = task_euid(proc->tsk); + t->sender_euid = proc->cred->euid; t->to_proc = target_proc; t->to_thread = target_thread; t->code = tr->code; @@ -4341,6 +4345,7 @@ static void binder_free_proc(struct binder_proc *proc) BUG_ON(!list_empty(&proc->delivered_death)); binder_alloc_deferred_release(&proc->alloc); put_task_struct(proc->tsk); + put_cred(proc->cred); binder_stats_deleted(BINDER_STAT_PROC); kfree(proc); } @@ -4799,6 +4804,7 @@ static int binder_open(struct inode *nodp, struct file *filp) get_task_struct(current->group_leader); proc->tsk = current->group_leader; mutex_init(&proc->files_lock); + proc->cred = get_cred(filp->f_cred); INIT_LIST_HEAD(&proc->todo); proc->default_priority = task_nice(current); binder_dev = container_of(filp->private_data, struct binder_device,